3054E Industrial Engine Fuel Injection Caterpillar


Fuel Injection
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1.1. Fuel Injection Pump
2.2. Delivery
3.2. Generation of High Pressure
4.2. Distribution and Injection
5.2. Timing
6.2. Shutoff
7.2. Control
8.1. Fuel Injection Nozzles


Illustration 1g01140556
Flow diagram of the fuel system
(1) Fuel injection nozzles
(2) Electronic fuel priming pump and secondary fuel filter
(3) Fuel injection pump
(4) Primary fuel filter/water separator
(5) Fuel tank
(6) Fuel return line
(7) Fuel supply line

The 3054E engine is equipped with a Bosch VP30 fuel injection pump. This pump is an axial piston distributor injection pump that is controlled by the Electronic Control Module (ECM).

The axial piston distributor injection pump generates injection pressure for all cylinders in a single pump. The injection pump is responsible for the distribution of fuel to the fuel injection nozzles. The injection pressure is generated by an axially moving piston. The movement of the piston is parallel to the fuel injection pump shaft.

When the engine is cranking, the fuel is pulled from fuel tank (5) through primary fuel filter/water separator (4) by fuel priming pump (2). When the fuel passes through the water separator, any water in the fuel will go to the bottom of the bowl. The fuel priming pump is equipped with a secondary fuel filter. From the fuel priming pump, the fuel passes through the fuel supply line to fuel injection pump (3). The fuel injection pump sends fuel through the high pressure fuel lines to fuel injection nozzles (1). The fuel injection nozzles spray atomized fuel into the cylinder.

The fuel injection pump needs fuel for lubrication. The precision parts of the pump are easily damaged. The engine must not be started until the fuel injection pump is full of fuel. The system must be primed when any part of the system is drained of fuel. The fuel system needs priming when a fuel filter is changed, and/or when a fuel line is removed, and/or when the fuel injection pump is replaced.

Fuel Injection Pump



Illustration 2g01140815
Schematic of the Bosch VP30 fuel injection pump
(1) ECM
(2) Electronic Control Unit (ECU) for the fuel injection pump
(3) Fuel priming pump
(4) Speed/timing sensor
(5) Cam ring
(6) Fuel solenoid valve
(7) Pressure regulator
(8) Distributor plunger
(9) Fuel transfer pump
(10) Fuel injection nozzle
(11) Timing solenoid valve
(12) Timing advance mechanism
(13) Roller
(14) Cam plate
(15) Delivery valve

The fuel injection pump has the following operations:

  • Delivery

  • Generation of high pressure

  • Distribution and injection

  • Timing

  • Shutoff

  • Control

Delivery



Illustration 3g01140827
Center view of the Bosch VP30 fuel injection pump
(9) Fuel transfer pump

Fuel is supplied by the head pressure of the priming pump. The fuel enters fuel transfer pump (9) of the fuel injection pump. The fuel transfer pump is a vane pump. The transfer pump is driven by the fuel injection pump shaft. The pump supplies a constant amount of fuel to the interior of the fuel injection pump. The revolution of the transfer pump is directly related to the speed of the fuel injection pump shaft.



Illustration 4g01140857
Fuel transfer pump for the Bosch VP30 fuel injection pump
(5) Cam ring
(16) Pump housing
(17) Outlet passage
(18) Rotor
(19) Vane
(20) Inlet passage

Rotor (18) rotates inside cam ring (5). The ring is firmly attached to pump housing (16). Vanes (19) are pressed against the ring by centrifugal force. The fuel flows through inlet passage (20) then into a recess in the pump housing.

The eccentric position of the rotor is relative to the cam ring. A volume is created between the vanes, the rotor, and the cam ring. The fuel is transported by the eccentric position. The eccentric position is relative to the rotor and outlet passage (17). The fuel is transfered to the outlet passage into the distributor plunger. The volume of the fuel is reduced between the inlet passage and the outlet passage. This creates pressure before the delivery to the distributor plunger.

The quantity of fuel increases as the speed of the engine increases. Increased engine speed increases the delivery pressure of the fuel. The pressure inside the pump is limited by a pressure regulator (7). The pressure regulator controls the fuel pressure. The fuel forces the valve spring open and the fuel flows back into the inlet passage from the inside of the fuel injection pump.

Generation of High Pressure



Illustration 5g01140929
The distributor rotor and the cam plate of the Bosch VP30 fuel injection pump
(5) Cam ring
(13) Roller
(14) Cam plate
(8) Distributor plunger
(21) Head of the distributor
(22) Springs

The fuel comes from the outlet passage of the fuel transfer pump (9). The high pressure is generated by the axial movement of the distributor plunger (8). The cam plate (14) is driven by the fuel injection pump shaft. The cam plate (14) has four cams. The number of cams corresponds to the number of cylinders of the engine. The cams on the cam plate (14) run on the rollers (13). The rollers (13) are fixed on the cam ring (5). The rotating movement and the lifting movement of the cam plate (14) generates high pressure.

The cam plate (14) moves the distributor plunger (8) toward the head of the distributor (21). The high pressure is created by a decrease in the volume between the distributor plunger (8) and the head of the distributor (21). The cam plate (14) is pressed to the cam ring (5) by two springs (22). This brings the distributor plunger (8) back to the original position. The fuel solenoid valve (6) closes the high pressure volume.

Distribution and Injection



Illustration 6g01140974
The rear view of the Bosch VP30 fuel injection pump
(6) Fuel solenoid valve
(15) Delivery valve
(11) Timing solenoid valve

The distribution of fuel to the fuel injection nozzles (10) takes place through the rotating movement of the distributor plunger (8). The fuel solenoid valve (6) meters the amount of fuel by the following operations:

  • Time of closure

  • Duration time

  • Start of injection

  • Amount of fuel


Illustration 7g01140988
Delivery of fuel from the delivery valve


Illustration 8g01141216
Closing of the delivery valve

The delivery valve (15) ensures that the pressure waves do not allow a reopening of the fuel injection nozzle (10). The pressure waves are created at the end of the injection process. The valve cone is lifted by the fuel pressure.

The fuel is forced through the fuel line to the fuel injection nozzle (10). The delivery ends and the fuel pressure drops. The valve spring presses the valve cone onto the valve seat. The reopening of a fuel injection nozzle (10) has a negative effect on emissions.

Timing

Retarding of the fuel injection is the direct relationship between the start of injection and the position of the piston. The timing compensates for the higher RPM of the engine by advancing the start of injection.



Illustration 9g01141217
Timing advance for timing mechanism (side view and top view)


Illustration 10g01366794
Timing retard for timing mechanism (side view and top view)

The timing advance or the timing retard of the fuel injection pump is shown in the following steps:

  1. The ECU (2) sends a signal to the timing solenoid valve (11).

  2. The timing mechanism is triggered by the timing solenoid valve (11).

  3. The timing solenoid valve (11) changes the pressure in the timing advance mechanism (12).

  4. The timing advance mechanism (12) changes the position of the cam ring (5).

  5. The cam ring (5) changes the position of the rollers (13).

  6. The rollers (13) change the position of the cam plate (14).

  7. The cam plate (14) changes the timing of the fuel delivery.

Shutoff

The engine shuts off by interrupting the fuel supply. The engine Electronic Control Module (ECM) (1) specifies the amount of fuel. The fuel solenoid valve (6) is switched by the ECU (2) on the fuel injection pump to zero.

Control



Illustration 11g01141220
Electronic control for the fuel system (typical example)

The ECU (2) for the injection pump uses the command from the ECM (1) and the measured values from the secondary speed/timing sensor (4) to actuate the fuel solenoid valve (6).



Illustration 12g01141235
The timing wheel and the secondary speed/timing sensor
(4) Secondary speed/timing sensor
(23) Timing wheel

The ECU (2) for the fuel injection pump is mounted on the top of the pump. The ECU has a connection to the engine ECM (2) and a connection to the speed/timing sensor (4). The ECU has a connection for the two solenoid valves (6). The ECM functions as a control computer. The ECU calculates the optimal parameters from the ECM data. The fuel solenoid (6) actuates the valve accordingly.

The secondary speed/timing sensor (4) in the fuel injection pump determines the precise angular position and the speed of the fuel injection pump shaft. Timing wheel (23) is permanently connected to the fuel injection pump shaft. The secondary speed/timing sensor (4) gets information from the timing wheel (23). The sensor then sends electrical impulses to the ECU (2). The ECU also uses the information to determine the average speed of the pump and momentary speed of the pump.

Note: The engine will not run if the secondary speed/timing sensor (4) fails.

The signal of the speed/timing sensor (4) is constant. Power command signals are routed over the CAN data link from the engine ECM (1) to the ECU (2) on the fuel injection pump.



Illustration 13g01141251
Operating principle
(24) Angle of fuel delivery
(25) Lift of the cam
(26) Stroke
(27) Pulse for actuating the fuel solenoid
(28) Valve lift
(29) Angle of the speed/timing sensor

The amount of fuel is proportional to the stroke of the piston. The effective stroke is proportional to the angle of fuel delivery. A temperature compensation takes place in the ECU (2). The compensation takes place in order to inject the precise amount of fuel.

Fuel Injection Nozzles



Illustration 14g01144089
Fuel injection nozzle

Each fuel injection nozzle is held into the cylinder head by a clamp around the fuel injection nozzle. The fuel injection nozzles are not serviceable but the nozzles can be removed in order to clean the orifice.

The fuel injection pump forces the fuel to flow under high pressure to the hole in the fuel inlet. The fuel then flows around a needle valve within the nozzle holder which causes the nozzle to fill with fuel. The pressure of the fuel pushes the needle valve and a spring. When the force of the fuel pressure is greater than the force of the spring, the needle valve will lift up.

When the needle valve opens, fuel under high pressure will flow through the nozzle orifices into the cylinder. The fuel is injected into the cylinder through the orifices in the nozzle end as a very fine spray. When the fuel is injected into the cylinder, the force of the fuel pressure in the nozzle body will decrease. The force of the spring will then be greater than the force of the fuel pressure that is in the nozzle body. The needle valve will move quickly to the closed position.

The needle valve has a close fit with the inside of the nozzle. This makes a positive seal for the valve.

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